Transformer-tap-changing device



31 1927' H. A. TRAVERS "630363 TRANSPORIBR TAP CHANGING DEVICE Filed June 16. 1926 Fly 1.

WITNESSES: mvsmon fiw, Henry/4. 77v

3 ea? WORN equipment is tinue to indicate the true Patented May 31, i927.

--.UNITED' s"Fa r's s;v PATENT-V or A.- TRAY E38, Q1" FOREST 'HII LS, PENNSYLVANIA, ASSIGNOB TO WESTING- H ANUFACTURING'GOMPANY, A CORPORATION OF PENNSYL- OUBE ELECTRIC & VLNIA.

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'rnansronmwar-cnanome nnvrcs.

Animation and June 10,

My invention relates to transformer-tap changing apparatus and particularly to relay systems for protecting such transformers. V

One object of my a protective system invention is to provide for an electrical tr'ansformer and tap-changing apparatus that shall protect the apparatus from conditions of short circuit within the transformer winding.

' Another object of my invention is to provide a difi'erential protective system for electricv transformers and tap-changing apparatusthat shall be controlled in accord- 5 ancefwith the operation of the tap-changing ap aratus. 1

nother object of my invention ig to provide a protective system for electrical transformers and tap-changing apparatus that 29 comprises an auto-transformer: the connections of which shall be controlled in accordance with the operation of theitap-changing apparatus. r 4

An electrical transformer is sometimes provided with a.'difi'erential relay system connectingthe primary and secondary circuits for the purpose of disconnecting it from its supply circuit in the event that the ratio between its input and output becomes of a magnitude that indicates a condition of a short-circuit between'the turns of its winding or a fault to groundf When a transformer having the above specified uipped also withetap-chang mg apparatus or varying the voltage 'ratio between the primary and secondary windings, it becomes necessary to provide means for varying the connections of' the relay system in order that such system shall conratio between the transformer input and theoutput,

-I accomplish the desired result by providing an auto-transformer inthe relay circuit,

one winding of which is energized from the primary circuit of the main transformer and the other winding of whichis energized from the secondary winding of the main transformer. three suitable current transv formers of fixed ratio, and varying the connections of the autotransformer n accordarioe with the changes in the voltage ratio of the main transformer.

"In the accompanying drawings, LFigure 1 is a diagrammatic View of on;

main transformer terrupter 6, to

automatically actuated um." Serial No. mean cuitsand apparatus embodying my invention; and i Fig. is a fragmentary form of my nvention. I My invention comprises, in general, a

1 aving the usual pri- -mary winding 2, a secondary winding 3 and a tap-changing device 4, together with a. relay protective system 5, embodying the details of my invention. The primary winding 2 ofthe main transformer 1 is connected. through a circuit ina supply circuit 7. The circuit interrupter 6 is provided with'the usual tripping coil 8. The. secondary winding 3 comprises a pair of parallel windings 9 and 11 that are connected, through an auto-balance transformer 12 and the tap-changing device .4, to a secondary circuit 13. The windings 9 and 11 areprovided with a plurality of taps 14 to 23 that cooperate with contact se ments. 24 to33 mountedon a drum 34 of the tap-changing device 4. The even numbered taps and contact segments cooperate with the winding 11, and ,the Odd numbered tap connections and contact segments coo era'te with the winding connected, by a shaft 35, to a motor '36'hav mg a reversing switch 37 connected to its fie d winding 38. For controlling the direcof the motor 36, the reversmay be either manually or by suitable circuits and apparatus which are not shown because they constitute no .part of the present invention.

The protective device 5 com rises'a current transformer 39, inductive y related to one of the conductors of the secondary circuit 13, and connected by conductors 41 and 42 to the several taps 43 to 53 of an autotransformer .54, whereby the current transformer 39 is in the secondary circuit thereof. A second current transformer 56 is connected, by the conductor 42 and a conduct0r57 to the primary winding 58 of the tion. of rotation mg switch 37 auto-transformer 54.

\Vhile an autotransf0rmer does not have separate primary and secondary windings, it is custon'iary practice to refer to the circuit'including the entire winding as the primary circuitand to the circuit including a portion of the winding as the secondary 9,. The drum 34 is circuit. Accordingly, the entire winding is hereinafter called the primary winding and that portion of the winding included in both circuits is called the secondary winding. A relay 59 is connected between the conductors 4:1 and 42 in parallel circuit to the autotransformer 54, across its secondary windft drum 61, having contact segments62 to 72 is mounted on an extension of the shaft 35 to cooperate with the transformer ta 5 43 to 53, l'eSl'lCCllVCl).

he relay. 59 may be of any desired type that operateswhen subjected to a predetermined current for a definite interval of time and comprises a winding 73 and a contactmaking device 7*. The contact-making device 74 is connected by conductors 75, to a battery 76 and the tripping coil 8 of the. circuit interrupter (3. The battery 75 is also connected, by conductors 77, to the motor 36.

Assuming the tap'changing device 4 to be in such position that the taps 1i and are in engagement with th contact segments 24 and 25, respectively, the'main secondary circuit 13 is completed through the balance-coil 12 and the tap-changing device 4, at. which time the contact segment 71' on the drum 61 is in engagement with the tap 52 of the auto-trarrsformer 34. The primary winding 58 of the alite-transformer 54 is energi ed in accordance with the current traversing the main primary winding 2, while the secondary winding of the autotransformer 54 includes all the windings above. the tap 52. The main transformer 1 is now in its .position of relatively low voltage and light secondary current, at which time the number of ampcre-turns'in the primary winding of the transformer 54 equals the number of ampere-turns in it; secondary winding, with the result that the protective winding 5 is in a state of equilibrium and no current traverses the relay 59.

\Vhen it is desired to increase the secondary current of the main transformer 1. the motor 16 is energized to turn the shaft in a counter-clockwise direction which causes the several contact segments to 33 to engage. the tap connections 15 to 23, respectively, in a manner wcll known in the art, and to increase the voltage and consequently. the secondary circuit in the main transformer 1. However. the current traversing the primary winding 2 of the main transformer 1 does not increase as fast as the current traversing its secondary circuit 13. Accordingly, if the setting of the autotransformer 54 were not changed. the infiuence of the current transformer 39 on the protective system would over-balance that of the primary-current transformer 56, with tlig result that the relay 59 would be operated to cause the circuit interrupter 6 to the number of ampere-turns in its secondary circuit. This is accomplished by causing the 'druni 61 to successively move the contact segments 71 to 62 into engagement with the tap connections 52 to 43, respectively, cordance with the novem'ent of the drum and the.contact segment carried thereby.

Under normal operating conditions, the auto-transformer 54 remains in a state of balance or equilibrium, and the relay 59 re-. mains deenergizcd. However, should ashort-circnit occur between the turns of the primary winding 2 or secondary winding 3, an increase in the amount of the primary current traversing the circuit 7 would occur, while the current traversing the secondary circuit 13 would not increase proportionately. The result of such condition isto cause the current transformer 56 to induce an increased current inthe primary winding 58 of the auto-transformer 54 that is notbalanced by the number of ampere-turns in the secondary circuit. Accordingly, the relay 59. is energized to close its contact-making de-' vice 74, thereby actuatingAhe tripping coil 8 to open the circuit interrupter 6.

\Vhen it is desired to reduce the secondary voltage of the transformer 1, the shaft 35 is turned in a. clockwise direction. which causes the contact segments on the drums'34' and G1 to engage their cooperating tap connections in a reverse order. However. the .num-- ber of ampere-turns in the primary circuit of the transformer 54 is always maintained equal to the number of secondary ampereturns. provided that no short-circuit exists between the turns of the main primary and secondary windings 2 and 3. respectively.

Referring to Fig. 2. I have shown a modified form of my invention in which the relay 59 is connected between the conductors=42 and 57; that is. across the current transformer connected to the primary circuit of the transformer 1. This form of my invention is otherwise similar to that shown in Fig. 1.

It. will thus be seen that I have provided a relay protective system for transformers having tap-changing apparatus connected thereto that is characterized by having auxihary tap-changing means for controlling' the connections of an auto-transformer, such in acthat the ratio of its primary and secondary ampere-turns remains equal, regardless of changes in the ratio of the 'mainprimary and secondary currents of the protected 5 transformer.

It is to be understood that such changes in the arrangement and conncction.of the component parts of my invention may be made as will be within the scope of the appended claims. r

I claim as my invention:

. 1..The combination with a transfor'mcrf comprising primary and secondary windings. means for varying the number of effective turns of one of the'windin s. and a- 2. The combination with a transformer comprising primary and secondary wind--' mgs, means for varying the number of efi'ec- 0 tive turns of one of the windings, nnd'a relay system responsive-to predeterm'ned differences in the currenttraversing the primary and secondary windings, of means for controlling the influence of the cnrncnts jraversing the primary and secondary windingsupon the relay system in accordance with the operation of the 'means for var ing the windings. j 3. The combination with a trans-former comprising primary and secondary wind: ings. means for varying the numberof effective turns of one of the windings, and a relay system responsive to predetermined differences in the current traversing the primary and secondary windings of a contact making device for controlling the influence of the currents traversing the primary and secondary windings upon the relay system in accordance with the operation of the means for varying the winding. I

4. The combination'with a main transformercomprising primary and secondary windings, means for varying the number of efi'ectiveturns of one of the windings, and

" a relay system comprising a second transformer and a relay responsive to predetermined differences in the current traversing the main primary and secondary windings, of means for controlling the influence of the currents traversing the main primary and sccondar windings. upontbe relav bv cont rolling the connections of the second trans former in accordance with theopcration of the means for varying the winding.

The con'ibination former comprising primary'and secondary windings. means for varying the. number of effective turns. of one of the windings. and a rcla system comprising an auto-transformer and a relay responsive to predeterareah relay connections of the auxiliary first named \vindin with a main trans "It connections of the autoa 6; The combination with a transformer comprising. fprimary and secondary windmgs, means tive turns of "one of'the windings. and a relay 'systcm re:ponsivc to predetermined differences in the currenttraversing the primary and secondary windings, and comprising an auxiliary transformer, and current transformers connected to the primary and secondary windings of the auxiliary transformer, of' means forcontrolling the influence of the currents traversing thefirst pained primary and secondary windin s system by controlling t e transformer in the operation of the means accordance with of the first-named windfor varying on Inga.

7.-T he' combination with a transformer comprising primary wand secondary windmgs, means for varying the number of effectivefturns of one of the windings, and a differences in the current traversing the pri- {nary and secondary windings. and comprismg' an auxiliary transformer; and current transformersconnected to. both primary and ,secondary windings, respectively, of means .for controlling the influence of the current traversing the first named primary and sec ondary windings upon the relay system by controlling the connections of the auxiliary transformer in accordance with the operation of the means for varying one of the,

8. The combinatiorr with comprising primary and secondary windings, means for varying the nmnber of effective turns of onc'of the windings, and a relay systemresponsive to predetermined differences in the current traversing the primary and secondary windings and comprising an auxiliary rent transformers connected to both primary and secondary windings. respectively of means for controlling the influence of the current traversing the first-named.primarv andsecondarv windings upon the relay svz tcmby varying the ratio between the primary and secondary windings of the auxiliary transformer in accordance with the operation of the means for varying one of the first-named windings.

In testimony whereof. I have hereunto subscribed my name this 2nd day of June,

HENRY A. TRAVERS.

or varying the number of etfec-- transformer and cur- .05 relay system responsive to predetermined a transformer 

